MIMICRY

During the course of their evolution, many unprotected species have come to resin ble distasteful ones that exhibit aposematic coloration. Two types of mimicry hav been identified: Batesian mimicry and Muellerian mimicry.
Batesian Mimicry. Batesian mimicry is named for W.H. Bates, a British natural 1st who first brought it to general attention in 1857. Bates discovered that iftheun protected (nonpoisonous) animals are present in numbers that are low relative n those of the species that they resemble, they will be avoided by predators. If them protected animals are too common, of course, many of them will be eaten by preda tors that have not yet learned to avoid individuals with particular characteristics.
In Batesian mimicry, unprotected species resemble others that are distasteful. Both species exhibit aposeroatic coloration. The unprotected mimics will be avoided by predators if they are relatively scarce.
Many of the best-known examples of Batesian mimicry occur among butterflies and moths. Obviously, predators in systems of this kind must use visual cues to tnuil for their prey, otherwise similar patterns of coloration would not matter to potential predators. Evidence is also increasing that Batesian mimicry can also involve ncuivi-sual cues, such as olfaction, although such examples are less obvious to humans.
The groups of butterflies that provide the models in Batesian mimicry are, w surprisingly, members of groups whose larvae feed on only one or a few closely related plant families, the plants on which they feed are strongly protected chemical!y. The model butterflies take poisonous molecules from these plants and retain themia their own bodies. The mimic butterflies, in contrast, belong to groups in which (b feeding habits of the larvae are not so restricted. As caterpillars, these butterflies b on a number of different plant families, but not those protected by toxic chemicals
One often-studied mimic among North American butterflies is the vicero. Limentitis archippus. This butterfly, which resembles the poisonu. monarch, ranges from central Canada south through much of the United States w of the Sierra Nevada and Cascade Range into Mexico. The larvae feed on willow cottonwoods, and neither the larvae nor the adults were thought to be distasteful to birds, although recent findings dispute this. Interestingly, the larvae of the vi^ are camouflaged on leaves because they resemble bird droppings, whereas thr tasteful larvae of the monarch are very conspicuous.

Muellerian Mimicry. Another kind of mimicry, Muellerian mimicry, was named for the German biologist Fritz Mueller, who first described it in 1878. In Muelii mimicry, several unrelated but protected animal species come to resemble one other- Thus different kinds of stinging wasps have yellow-and-black striped aK-mens, but they may not all be descended from a common ancestor that had similar coloration. In general, yellow-and-black and bright red tend to be common color patterns that presumably warn predators relying on vision that animals with such coloration are to be avoided. It is more difficult to prove that a resemblance between two protected animals actually represents Muellerian mimicry than it is to demonstrate Baiesian mimicry experimentally.
In both Batesian and Muellerian mimicry, mimic and model must not only look alike but also act alike if predators are to be deceived. For example, the members of several families of insects that resemble wasps behave surprisingly like the wasps they mimic, flying often and actively from place to place. Mimics must also spend most of their time in the same habitats as do their models; such collective living provides a greater learning signal for potential predators- If they did not, predators would discover that all of those conspicuous animals are not only easily seen but also quite tasty! If animals that resemble one another are all poisonous or dangerous, they still gain inadvantage by resembling one another, thus achieving collective protection.
In Muellerian mimicry, two or more unrelated but protected species resemble one another, thus achieving a kind of group defense.